Central vacuum cleaning systems are widely used in a number of different facilities such as stables, warehouses, hotels, and private accommodations. Vehicles such as trains, airplanes, busses and boats are also subject for the implementation of central vacuum cleaning systems. Generally such central vacuum cleaning systems are assembled during the construction of the building or the vehicle, however not so uncommon; a central vacuum cleaning system can be installed afterwards by tearing down parts of the walls, ceilings or floors to incorporate the pipelines of the vacuum cleaning system. In either case, the assembling of the pipeline, which in almost all cases extends inside the walls, ceilings or floors are in most cases done under a tight time schedule. Clients pay per hour or in cases where a fixed rate is set, the installer of the system is driven to minimize the installation time for optimizing the profit. These driving forces tend to increase the demand for quality control and the demand on equipment to be easy and flexible to install. Such equipment can be pipelines which are easy and flexible to install, which do not leak and which provide an installer with the possibility to make amendments after installation, e.g. if some item or the installation is proven to be defect.
Additionally, one of the reasons which central vacuum cleaning systems is widely used is that they provide a quiet vacuum cleaning, with substantially no air contamination. The main reason for this being that the central vacuum cleaning unit, which suck air, is not arranged in the same room as where the actual cleaning takes place. It should be noted however, that these cleaning systems are not silent; indeed there is what can be called a noise pollution due to turbulent air flow through the pipelines. The turbulence, and the noise pollution, is affected by the couplings, air flow velocity, pipeline flow resistance and dimensions of the pipelines, pipe isolation etc. However, the above mentioned issues seem to not yet have been properly solved by the industry.
One attempt to provide pipes which provide tight seals is described in the publication of U.S. Pat. No. 5,547,230, in which a force transmitting joint is formed between two pipe sections. The pipe ends comprise a variable wall thickness so that they can be joined with mating pipe ends. Although the solution is said to provide a tight seal, the solution do not provide for a sufficiently low noise pollution, with respect to fluid flow through the pipelines. Further in U.S. Pat. No. 4,664,421 is a leak resistant pipe joint provided to joint plastic pipes of at least four inches in diameter. The pipe joint comprises a flexible gasket with projecting ribs. The solution seems to provide for a tight seal, but lack solutions and the insight of providing a low noise fluid flow through the pipeline.
Other existing vacuum pipe lines and pipe couplings uses PVC pipes and PVC pipe couplings. Adhesive is used to attach the pipes and the pipe couplings. Not only is PVC an environmentally less desired material, the adhesive complicates the assembly of the pipes. It has been shown that adhesive connections are more susceptible to noise pollution than adhesive free connections. The main reason being that adhesive have a tendency to protrude out from the connection (between the pipe and the pipe coupling) and into the pipe, when the pipe and the pipe coupling is pushed together.
It is an object of the present invention to at least partly solve the above mentioned drawbacks. More specifically it is an object of the present invention to at least partly provide a solution with reduces the noise of fluid flow in the pipelines, while at the same time partly provides a pipe coupling which enables easy and flexible assembly of a vacuum pipe line.